Update README.md
sys: ps2kbd: handle extended scancodes

Bit of a hack.
ports: add doom to base system
Squashed 'ports/doom/' content from commit d26d26668

git-subtree-dir: ports/doom
git-subtree-split: d26d266689a43b3f4e099d3b248213b96e34998a
intro(1): fix typo
ports: don't install info files for make
Makefile: install src to /usr/src
bin: install sbase man pages
ports: install devel by default

And drop optional ports system entirely
README.md: clarify where third-party software is used
sys/vt: force cursor shown if not blinking
usr.share: make install directories
Compress initramfs with gzip

Implements a suitable decompressor in boot/efi; for multiboot it's
handled by the stage 1 bootloader.
Integrate zlib into build system
Squashed 'vendor/zlib/' content from commit 51b7f2abd

git-subtree-dir: vendor/zlib
git-subtree-split: 51b7f2abdade71cd9bb0e7a373ef2610ec6f9daf
Bump FAT size to 128M, add option to strip bins
/sbin/getty: populate environment
usr.share: add boot(7)